This invention relates to a method of measuring the concentration of a solute in a solute stream.
The concentration of a solute component of a liquid can be difficult to monitor when the solute lacks an easily measurable property. For example, the addition of high molecular weight poly(ethylene oxide) ([--OCH.sub.2 CH.sub.2 --]) (POLYOX.TM.) to turbulent water systems has been reported to enhance stream properties by reducing frictional drag and increasing volumetric flow rate. However, it is difficult to directly monitor the POLYOX.TM. concentration, e.g., in a flowing stream of water. Similarly, it is difficult to detect the concentration of aqueous film forming formulation (AFFF), an agent used to combat aviation fires, and other solutes.
One method of determining solute concentration involves the use of indicators with a high refractive index, such as diethylene glycol butyl ether (DBGE), that are mixed with the solute component. The concentration of the solute component can be determined by determining the refractive index of the solute stream. However, these indicators can be expensive and environmentally undesirable, and large amounts of such indicators, e.g., 20% (vol/vol) of DBGE in an AFFF solution, are typically added to the solute stream.